The present invention relates to a color corrector, a signal converter, a video display using the corrector and the converter, and a method of adjusting the display suitable for a gamma correction and a white balance adjustment related to a video signal processing in a video apparatus such as a video display, a television receiver, a printer, or a camera.
In this connection, the term "color corrector" adopted in this specification is defined to include apparatuses which conduct, in addition to the color correction of signals of three primary colors including red, green, and blue, the video signal correction and gradation correction for video displays handling monochrome and black-and-white video signals.
There has been known a gamma correction circuit for a display, a video camera, or the like, for example, as shown in FIG. 2 of the Japanese Utility Model application publication No. JP-U-63-47113. In the gamma correction circuit of this diagram, assuming a relationship Va&lt;Vb&lt;Vc&lt;Vd between potential values Va, Vb, Vc, and Vd respectively of the power sources 30, 33, 36, and 39, a conductive state is respectively established in diodes 32, 35, 38, and 41 as a voltage applied on an input terminal 1 is increased.
Consequently, when a voltage signal having a waveform 42 of FIG. 3 of the utility model publication above is applied to the input terminal 1, there is attained from an output terminal 5 an inverse output signal having a waveform 43 which can be approximated to a .gamma.-th power of the input signal. In consequence, using a gamma correction circuit of FIG. 2, there can be approximately obtained a proportional relationship between an input light quantity and an output light quantity respectively of the transmission and reception systems.
However, according to the gamma correcting circuit described in the JP-U-63-47113, the .gamma.-th power transfer characteristic is implemented as indicated by a broken-line approximation and hence there cannot be sufficiently attained a satisfactory correction precision. This makes it difficult to develop a high-fidelity reproduction of colors between the video sending and receiving systems. In addition, when it is desired to cope with changes in the parameter .gamma. associated with correction due to variation in devices or the like, there is required alteration in values of a large number of constituent elements. Namely, this is impossible in practices.